Conventional meat grinders in the past have utilized a screw type conveyor for advancing meat particles through a chamber to force them through a grinder plate which is disposed at the end of the chamber. The grinder plate normally has a plurality of orifices disposed therethrough for reducing the particulate size of the meat. Normally, grinding is begun with baseball size chunks of meat and then reduced to a desired size which may take several stages of grinding.
Screw type meat grinders require a defined clearance between the screw conveyor and the sides of the chamber through which the meat is passed. This clearance allows the screw conveyor to clear the walls while rotating. However, this clearance allows meat to flow backwards around the screw conveyor under high pressure conditions, thereby reducing the maximum amount of pressure that can be applied to the meat particles at the grinder plate. This pressure limit defines the maximum flow rate of meat that can be passed through a grinder plate. In addition, gristle or bone chips that may be present in the meat may clog the grinder plate and further inhibit grinding.
In grinding the meat to a desired particle size in a large manufacturing environment, it has been necessary to change grinder plates at various stages of the operation. Since it is very difficult to go from a large particulate size to a very small particulate size, a number of stages are necessary. When the meat is output from the grinder plate, it takes on a very "stringy" texture since the fat and meat fibers have a tendency to adhere together along the longitudinal direction. Therefore, the grinding operation requires an additional step to reduce the length of this material. All of these operations must be repeated for each stage of grinding.
These problems have been addressed in U.S. Pat. No. 1,611,244 issued to Schmidt on Dec. 21, 1926. Schmidt discloses a grinder that utilizes a piston to advance the meat in the chamber towards the grinder plate. A rotating grinder knife is supplied adjacent the grinder plate to rotate thereabout. An electric motor is provided to rotate the knife through a shaft. To place meat into the chamber, the grinder plate must be removed and then replaced.
In view of the above disadvantages, there exists a need for a meat grinder that supplies a continuous flow of meat at a high pressure with a variable particulate size output.